The invention relates to a process for the preparation of an aliphatic C2-C14 hydrocarbon product, such as a hydrocarbon in the liquefied petroleum gas (LPG) and gasoline distillation range, from a natural fat or derivative thereof.
In order to meet an increasing demand for fuels in general and ecological fuels in particular, producers have started to prepare liquid hydrocarbon fuels from biological sources. If such biological fuels can be prepared easily and in good quality, they become an attractive alternative for the increasingly scarce mineral oil based fuels. At the same time, their burden on the environment will be smaller. Natural fats and derivatives thereof contain long hydrocarbon chains and are therefore considered to be the best raw materials for hydrocarbon fuels of biological origin.
Natural fats are substances consisting of one or more triesters of glycerine and fatty acids, so called triglycerides. Derivatives of natural fats are generally fatty acids, other fatty acid esters, fatty alcohols, their chemical analogues and derivatives. Biological fuels have traditionally been prepared from natural fats and derivatives thereof by transesterification, deoxygenation and different types of cracking.
The preparation of diesel fuel from natural fats or derivatives thereof has been studied extensively. Among others, FI 100248, EP 1396531 B1, U.S. Pat. No. 7,279,018 B2, EP 1681337 A1, EP 1741767 A1, EP 1741768 A1, EP 1795576 A1 and WO 2008157465 describe processes for producing diesel hydrocarbons and are incorporated herein by reference in their entireties.
The preparation of lower aliphatic C2-C14 hydrocarbons such as gasoline from natural fats or derivatives thereof has been studied very little. GB 339048 feeds heated gaseous soya bean oil together with hydrogen over a catalyst and obtains gasoline or benzine-like hydrocarbons. U.S. Pat. No. 2,163,563 passes a mixture of fat and mineral oil over a Ni catalyst at 20 MPa and 360° C. converting the fat into corresponding hydrocarbons, and separating the hydrocarbons from the mineral oil by distillation. These patent references, GB 339048 and U.S. Pat. No. 2,163,563, are incorporated herein by reference in their entireties.
GB 1524781 pyrolyses vegetable oil catalytically and obtains liquid hydrocarbons as well as gaseous hydrocarbons containing 50-70 volume-% of lower olefins. U.S. Pat. No. 5,233,109 cracks natural oil into crude petroleum at 420-550° C. and 0.1-1.0 MPa using a 1-10-fold amount of alumina based catalyst. These patent references, GB 1524781 and U.S. Pat. No. 5,233,109, are incorporated herein by reference in their entireties.
Conventional preparations of aliphatic C2-C14 hydrocarbons from natural fats or derivatives thereof are mostly uncontrolled cracking methods. Applicant has found that, in addition to the above-mentioned olefins, considerable amounts of aromatic hydrocarbons and coke are formed. Such by-products are harmful to the catalysts. In addition, the natural fats and their derivatives contain heteroatomic impurities which cannot be effectively removed by conventional methods.
In view of the above, the main objective of the invention is to provide an alternative process for the preparation of aliphatic C2-C14 hydrocarbons from natural fats or derivatives thereof. More specifically, an objective of the invention is to prepare aliphatic C2-C14 hydrocarbons from natural fats or derivatives thereof with improved yield and octane number. Still further objectives of the invention are to prepare aliphatic C2-C14 hydrocarbons from natural fats or derivatives thereof with minimal formation of olefins, aromatics, coke and other impurities. Finally, a process is aimed at which enables the preparation of C2-C14 hydrocarbons of biological origin with a minimum of resources.